Polymerizable monomer compound, liquid crystal composition, and liquid crystal display device

ABSTRACT

A novel polymerizable monomer compound that can be used for a variety of liquid crystal devices is provided. Particularly, a novel liquid crystal composition including the novel polymerizable monomer compound and exhibiting a blue phase is provided. Further, a liquid crystal display device manufactured with the use of the liquid crystal composition is provided. A polymerizable monomer compound represented by the following general formula (G1) is provided. In the general formula (G1), n and m are individually an integer from 1 to 20 and may be the same as or different from each other, and R 1  and R 2  individually represent hydrogen or a methyl group.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention disclosed in this specification relates to a polymerizablemonomer compound, a liquid crystal composition including thepolymerizable monomer compound, a liquid crystal display deviceincluding the polymerizable monomer compound, and manufacturing methodsthereof.

2. Description of the Related Art

In recent years, flat panel displays have been put to practical use andhave been substituted for conventional displays using cathode-ray tubes.The flat panel displays include liquid crystal display devices whichhave liquid crystal elements, EL display devices which have electroluminescent elements (EL elements), plasma displays, and the like, andthey come into competition in the market. Liquid crystal display devicesestablish a position of superiority by overcoming disadvantages andsuppressing production cost with use of a variety of techniques.

As a constituent of a liquid crystal composition used for a liquidcrystal display device, a polymerizable monomer compound is used. Forexample, polymer dispersed liquid crystal (PDLC) or polymer networkliquid crystal (PNLC) has a structure in which liquid crystal grains aredispersed in a polymer layer which forms a polymer network, and a whiteimage (a bright image) is displayed using scattered light by liquidcrystal. A polymerizable monomer compound is used as a material of thepolymer layer.

Further, in the case where a display mode using liquid crystalexhibiting a blue phase is employed as a display mode of liquid crystal,a polymerizable monomer compound is used in some cases. It has beenreported that a liquid crystal composition which includes apolymerizable monomer compound and a liquid crystal material exhibitinga blue phase is subjected to polymer stabilization treatment by which apolymerizable monomer compound is polymerized, so that the temperaturerange where a blue phase is exhibited is expanded (for example, seePatent Document 1).

Furthermore, a polymerizable monomer compound is also used as a materialof an optical film which is provided to, for example, achieve a wide,viewing angle and improvement in contrast in a display portion of aliquid crystal display device (for example, see Patent Document 2).

REFERENCE

-   [Patent Document 1] PCT International Publication no 2005-090520-   [Patent Document 1] Japanese Published Patent Application no.    2008-50440

SUMMARY OF THE INVENTION

An object is to provide a novel polymerizable monomer compound that canbe used for a variety of liquid crystal devices.

Another object is to provide a novel liquid crystal compositionincluding the novel polymerizable monomer compound or a liquid crystaldisplay device manufactured with the use of the liquid crystalcomposition.

An embodiment of the present invention is a polymerizable monomercompound represented by the following general formula (G1).

In the general formula (G1), n and m are individually an integer from 1to 20, and R¹ and R² individually represent hydrogen or a methyl group.

Another embodiment of the present invention is a polymerizable monomercompound represented by the following general formula (G2).

In the general formula (G2), n and are individually an integer from 1 to20.

Another embodiment of the present invention is a polymerizable monomercompound represented by the following general formula (G3).

Note that in the general formula (G3), n and m are the same integer from1 to 20, and R¹ and R² individually represent hydrogen or a methylgroup.

Another embodiment of the present invention is a polymerizable monomercompound represented by the following general formula (G4).

In the general formula (G4), n and m are the same integer from 1 to 20.

Another embodiment of the present invention is a liquid crystalcomposition including any one of the polymerizable monomer compoundsgiven above.

Another embodiment of the present invention is a liquid crystalcomposition including any one of the polymerizable monomer compoundsgiven above, a nematic liquid crystal compound, and a chiral agent.

The liquid crystal compositions may exhibit a blue phase.

Another embodiment of the present invention is a liquid crystal displaydevice including any of the above-described liquid crystal compositions.

A novel polymerizable monomer compound can be provided. A novel liquidcrystal composition including the novel polymerizable monomer compoundcan be provided.

A liquid crystal display device manufactured with the use of the liquidcrystal composition can be provided. The liquid crystal display devicecan be driven at a low voltage, leading to a reduction in powerconsumption of the liquid crystal display device.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIGS. 1A and 1B are conceptual diagrams each illustrating a liquidcrystal compound and a liquid crystal composition;

FIGS. 2A and 2B are diagrams illustrating one mode of a liquid crystaldisplay device;

FIGS. 3A to 3D are diagrams each illustrating one mode of an electrodestructure of a liquid crystal display device;

FIGS. 4A1, 4A2, and 4B are diagrams illustrating liquid crystal displaymodules;

FIGS. 5A to 5F are diagrams each illustrating an electronic apparatus;

FIGS. 6A to 6C are ¹H NMR charts of Dac-PEPEP-F-O6;

FIG. 7 is a graph showing an absorption spectrum of Dac-PEPEP-F-O6 in adichloromethane solution of Dac-PEPEP-F-O6; and

FIG. 8 is a graph showing a relation between applied voltage andtransmittance in a liquid crystal element in Example 2.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiments of the present invention will be described withreference to the drawings. Note that the present invention is notlimited to the description given below, and modes and details of thepresent invention can be modified in various ways without departing fromthe spirit and scope of the present invention. Therefore, the presentinvention should not be construed as being limited to the description inthe following embodiments. In the structures to be given below, the sameportions or portions having similar functions are denoted by the samereference numerals in different drawings, and explanation thereof willnot be repeated.

In addition, a liquid crystal display device in this specification andthe like refers to an image display device, a display device, or a lightsource (including a lighting device). Furthermore, the liquid crystaldisplay device also includes the following modules in its category: amodule to which a connector such as a flexible printed circuit (FPC), atape automated bonding (TAB) tape, or a tape carrier package (TCP) isattached; a module having a TAB tape or a TCP at the tip of which aprinted wiring board is provided; and a module in which an integratedcircuit (IC) is directly mounted on a display element by chip on glass(COG) method. Note that a liquid crystal display device in thisspecification and the like refers to any type of electronic apparatuswhich utilizes liquid crystal characteristics; for example, a liquidcrystal electro-optical device without display function is included inits category.

Embodiment 1

In this embodiment, a novel polymerizable monomer compound according toan embodiment of the present invention will be described.

A polymerizable monomer compound according to an embodiment of thepresent invention is a polymerizable monomer compound represented by thegeneral formula (G1).

In the general formula (G1), n and m are individually an integer from 1to 20, and may be the same as or different from each other, and R¹ andR² individually represent hydrogen or a methyl group.

Another embodiment of the present invention is a polymerizable monomercompound represented by the following general formula (G2).

In the general formula (G2), n and m are individually an integer from 1to 20, and may be the same as or different from each other.

Another embodiment of the present invention is a polymerizable monomercompound represented by the following general formula (G3).

Note that in the general formula (G3), n and to are the smile integerfrom 1 to 20, and R¹ and R² individually represent hydrogen or a methylgroup.

In the general formula (G3), R¹ and R² are preferably hydrogen foreasier synthesis. Therefore, another embodiment of the present inventionis a polymerizable monomer compound represented by the following generalformula (G4).

In the general formula (G4), n and mare the same integer from 1 to 20.

Specific examples of polymerizable monomer compounds represented by thegeneral formula (G1) include polymerizable monomer compounds representedby the structural formulae (100) to (144). Note that the presentinvention is not limited thereto.

A variety of reactions can be applied to a method of synthesizing thepolymerizable monomer compound of this embodiment. For example, thepolymerizable monomer compound can be synthesized by a synthesisreaction in Synthesis Method 1 or Synthesis Method 2.

<Synthesis Method 1>

In Synthesis Method 1, a synthesis method of a polymerizable monomercompound represented by the general formula (G1) will be described withreference to the following reaction formulae (A-1) and (A-2).

An esterification reaction of 1,4-benzenediol (Compound 1) and a benzoicacid derivative (Compound 2) is performed, whereby a hydroxyphenylderivative (Compound 3) can be obtained (reaction formula (A-1)). In thereaction Formula (A-1), n and m are individually an integer from 1 to20, and R¹ and R² individually represent hydrogen or a methyl group.

As the esterification reaction, an esterification reaction in whichdehydration condensation using an acid catalyst is performed(addition-elimination reaction) is given. In the case where adehydration condensation reaction is performed, an acid catalyst such asconcentrated sulfuric acid or para-toluenesulfonic acid,1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochroride(abbreviation: EDC), dicyclohexyl carbodiimide (abbreviation: DCC) canbe used. In the case where EDC or DCC is used, EDC is preferable becausea by-product can be easily removed. The synthesis of Compound 3 is notlimited to such reactions.

Next, an esterification reaction of hydroxyphenyl derivative (Compound3) obtained by the reaction formula (A-1) and benzoic acid derivative(Compound 4) is performed, whereby the polymerizable monomer compoundrepresented by the general formula (G1), which is a target substance,can be obtained (reaction formula (A-2)). In the reaction formula (A-2),n and m are individually an integer from 1 to 20, and R¹ and R²individually represent hydrogen or a methyl group.

As the esterification reaction, an esterification reaction in whichdehydration condensation using an acid catalyst is performed(addition-elimination reaction) is given. In the case where adehydration condensation reaction is performed, an acid catalyst such asconcentrated sulfuric acid or para-toluenesulfonic acid,1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochroride(abbreviation: EDC), dicyclohexyl carbodiimide (abbreviation: DCC) canbe used. In the case where EDC or DCC is used, EDC is preferable becausea by-product can be easily removed. The synthesis of the polymerizablemonomer compound represented by the general formula (G1) is not limitedto such reactions.

<Synthesis Method 2>

In Synthesis Method 2, a synthesis method of a polymerizable monomercompound according to an embodiment of the present invention in the casewhere n and m are the same integer, and R¹ and R² are the samesubstituent in the general formula (G1) will be described.

An esterification reaction of one equivalent of 1,4-benzenediol(Compound 1) and two equivalents of a benzoic acid derivative (Compound2) is performed, whereby the polymerizable monomer compound representedby the general formula (G5), which is a target substance, can beobtained (reaction formula (B-1)). In the reaction formula (B-1), n isan integer from 1 to 20, and R¹ represents hydrogen or a methyl group.

As the esterification reaction, an esterification reaction in whichdehydration condensation using an acid catalyst is performed(addition-elimination reaction) is given. In the case where adehydration condensation reaction is performed, an acid catalyst such asconcentrated sulfuric acid or para-toluenesulfonic acid,1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochroride(abbreviation: EDC), dicyclohexyl carbodiimide (abbreviation: DCC) canbe used. In the case where EDC or DCC is used, EDC is preferable becausea by-product can be easily removed. The synthesis of the polymerizablemonomer compound represented by the general formula (G5) is not limitedto such reactions.

In the above manner, the polymerizable monomer compound according tothis embodiment can be synthesized.

The polymerizable monomer compound described in this embodiment can beused as a constituent of a liquid crystal composition. Further, avariety of liquid crystal display devices can be manufactured with theuse of a liquid crystal composition including the polymerizable monomercompound described in this embodiment.

Note that the structures, methods, and the like described in thisembodiment can be combined as appropriate with any of the structures,methods, and the like described in the other embodiments.

Embodiment 2

In this embodiment, a liquid crystal composition including thepolymerizable monomer compound described in Embodiment 1, in particular,a liquid crystal composition including the polymerizable monomercompound described in Embodiment 1 and exhibiting a blue phase will bedescribed.

A liquid crystal composition described in this embodiment includes anematic liquid crystal compound, the polymerizable monomer compoundrepresented by the general formula (G1) in Embodiment 1, and a chiralagent.

The nematic liquid crystal compound is not particularly limited, andexamples thereof are a biphenyl-based compound a terphenyl-basedcompound, a phenylcyclohexyl-based compound, a biphenylcyclohexyl-basedcompound, a phenylbicyclohexyl-based compound, a benzoic acidphenyl-based compound, a cyclohexyl benzoic acid phenyl-based compound,a phenyl benzoic acid phenyl-based compound, a bicyclohexyl carboxylicacid phenyl-based compound, an azomethine-based compound, an azo andazoxy based compound, a stilbene-based compound, a bicyclohexyl-basedcompound, a phenylpyrimidine based compound, a biphenylpyrimidine-basedcompound, a pyrimidine-based compound, and a biphenyl ethyne-basedcompound.

A liquid crystal composition according to this embodiment includes thepolymerizable monomer compound represented by the general formula (G1)in Embodiment 1. Note that the liquid crystal composition according tothis embodiment may include one or more types of the polymerizablemonomer compounds represented by the general formula (G1).

Note that among the polymerizable monomer compounds represented by thegeneral formula (G1), use of a polymerizable monomer compound in which nand m are individually an even number from 2 to 20 (e.g., polymerizablemonomer compound represented by the structural formula 101, thestructural formula 121, or the structural formula 143 in Embodiment 1)for a liquid crystal composition is preferable. This is because thetreatment temperature range where an alignment state of a blue phase isstable in polymer stabilization treatment for a blue phase can bewidened, or a polymer-stabilized blue phase which causes less residualbirefringence and thus has high reliability to successive voltageapplication can be easily obtained.

The liquid crystal composition described in this embodiment may includeanother polymerizable monomer compound, in addition to the polymerizablemonomer compound represented by the general formula (G1). Thepolymerizable monomer compound may be a monofunctional monomer such asacrylate or methacrylate; a polyfunctional monomer such as diacrylate,triacrylate, dimethacrylate, or trimethacrylate; or a mixture thereof.Further, the polymerizable monomer compound may have liquidcrystallinity, non-liquid crystallinity, or both of them. Further, apolymerization initiator May be added to the liquid crystal composition

As the polymerization reaction, photopolymerization reaction orthermopolymerization reaction may be employed, and photopolymerizationreaction is preferred. In particular, photopolymerization reaction withultraviolet light is preferred. Therefore, as a polymerizationinitiator, acetophenone, benzophenone, benzoin, benzil, michler'sketone, benzoin alkyl ether, benzil dimethylketal, or thioxanthone canbe used as appropriate, for example. Note that after the polymerstabilization treatment, the polymerization initiator becomes animpurity that does not contribute to operation of a liquid crystaldisplay device in the polymer-liquid crystal composite; therefore, theamount of the polymerization initiator is preferably as small aspossible. For example, the amount of the polymerization initiator ispreferably less than or equal to 0.5 wt % in the liquid crystalcomposition.

The liquid crystal composition described in this embodiment may includea chiral agent, in addition to the above-described nematic liquidcrystal compound, the polymerization monomer compound represented by thegeneral formula (G1), and polymerization initiator. The chiral agent isused to induce twisting of the liquid crystal composition, align theliquid crystal composition in a helical structure, and make the liquidcrystal composition exhibit a blue phase. For the chiral agent, acompound which has an asymmetric center, high compatibility with theliquid crystal composition, and strong twisting power is used. Inaddition, the chiral agent is an optically active substance; a higheroptical purity is better and the most preferable optical purity is 99%or higher.

The additive amount of the chiral agent influences the diffractionwavelength of the liquid crystal material exhibiting a blue phase.Therefore, the additive amount of the chiral agent is preferablyadjusted so that the diffraction wavelength of the liquid crystalmaterial exhibiting a blue phase is out of a visible region (380 nm to750 nm). As the chiral agent, S-811 (produced by Merck Ltd., Japan),S-1011 (produced by Merck Ltd., Japan),1,4:3,6-dianhydro-2,5-bis[4-(n-hexyl-1-oxy)benzoic acid]sorbitol(abbreviation: ISO-(6OBA)₂) (produced by Midori Kagaku Co., Ltd.), orthe like can be selected as appropriate.

The liquid crystal composition which is an embodiment of the presentinvention includes the above-described materials. Note that apolymer-liquid crystal composite which has been subjected to polymerstabilization treatment and includes the above materials is included inthe category of the liquid crystal composition which is an embodiment ofthe present invention.

This polymer stabilization treatment may be performed on a liquidcrystal composition exhibiting an isotropic phase or a liquid crystalcomposition exhibiting a blue phase under the control of thetemperature. A temperature at which the phase changes from a blue phaseto an isotropic phase when the temperature rises, or a temperature atwhich the phase changes from an isotropic phase to a blue phase when thetemperature falls is referred to as the phase transition temperaturebetween a blue phase and an isotropic phase. For example, the polymerstabilization treatment can be performed in the following manner: aftera liquid crystal composition is heated to exhibit an isotropic phase,the temperature of the liquid crystal composition is gradually loweredso that the phase changes to a blue phase, and then, light irradiationis performed while the temperature at which a blue phase is exhibited iskept.

With the use of the liquid crystal composition described in thisembodiment for a liquid crystal element, low voltage driving of theliquid crystal element can be achieved. Further, with the use of theliquid crystal element for a liquid crystal display device, a reductionin power consumption of the liquid crystal display device can beachieved.

Note that the structures, methods, and the like described in thisembodiment can be combined as appropriate with any of the structures,methods, and the like described in the other embodiments.

Embodiment 3

In this embodiment, a liquid crystal element and a liquid crystaldisplay device to which the polymerizable monomer compound described inthe above embodiments or a liquid crystal composition including thepolymerizable monomer compound is applied will be described withdrawings.

FIGS. 1A and 1B each illustrate an example of a liquid crystal elementand a liquid crystal display device according to this embodiment.

Note that in this specification and the like, a liquid crystal elementis an element which controls transmission or non-transmission of lightby an optical modulation action of liquid crystal and includes at leasta pair of electrode layers and a liquid crystal composition interposedtherebetween. The liquid crystal element described in this embodimentincludes at least a pair of electrode layers (the pixel electrode layer230 and the common electrode layer 232 having different potentials), anda liquid crystal composition 208 including the polymerizable monomercompound represented by the general formula (G1) in Embodiment 1 betweenthe pair of electrode layers. In this embodiment, the liquid crystalcomposition capable of exhibiting a blue phase described in Embodiment 2is used as the liquid crystal composition 208.

FIGS. 1A and 1B each illustrate a liquid crystal element and a liquidcrystal display device in which the liquid crystal composition 208,which is a liquid crystal composition exhibiting a blue phase, isprovided between a first substrate 200 and a second substrate 201. Adifference between the liquid crystal element and the liquid crystaldisplay device in FIG. 1A and those in FIG. 1B is positions of the pixelelectrode layer 230 and the common electrode layer 232 with respect tothe liquid crystal composition 208.

In the liquid crystal element and the liquid crystal display deviceillustrated in FIG. 1A, the pixel electrode layer 230 and the commonelectrode layer 232 are adjacently provided between the first substrate200 and the liquid crystal composition 208. With the structure in FIG.1A, a method in which the gray scale is controlled by generating anelectric field substantially parallel (i.e., in the lateral direction)to a substrate to move liquid crystal molecules in a plane parallel tothe substrate can be used.

The structure in FIG. 1A can be favorably applied to the case where theliquid crystal composition exhibiting a blue phase, which is a liquidcrystal composition according to an embodiment of the present invention,is used as the liquid crystal composition 208. The liquid crystalcomposition provided as the liquid crystal composition 208 may containan organic resin.

With an electric field generated between the pixel electrode layer 230and the common electrode layer 232, liquid crystal is controlled. Anelectric field in the lateral direction is generated in the liquidcrystal, so that liquid crystal molecules can be controlled by theelectric field. The liquid crystal composition exhibiting a blue phaseis capable of quick response. Thus, a high-performance liquid crystalelement and a high-performance liquid crystal display device can beachieved. That is, the liquid crystal molecules aligned to exhibit ablue phase can be controlled in the direction parallel to the substrate,whereby a wide viewing angle can be obtained.

For example, such a liquid, crystal composition exhibiting a blue-phase,which is capable of quick response, can be favorably used for asuccessive additive color mixing method (field sequential method) inwhich light-emitting diodes (LEDs) of RGB or the like are arranged in abacklight unit and color display is performed by time division, or athree-dimensional display method using a shutter glasses system in whichimages for the right eye and images for the left eye are alternatelyviewed by time division.

In the liquid crystal element and the liquid crystal display deviceillustrated in FIG. 1B, the pixel electrode layer 230 and the commonelectrode layer 232 are provided on the first substrate 200 side and thesecond substrate 201 side respectively, with the liquid crystalcomposition 208 interposed therebetween. With the structure in FIG. 1B,a method in which the gray scale is controlled by generating an electricfield substantially perpendicular to a substrate to move liquid crystalmolecules in a plane perpendicular to the substrate cane be used. Analignment film 202 a may be provided between the liquid crystalcomposition 208 and the pixel electrode layer 230 and an alignment film202 b may be provided between the liquid crystal composition 208 and thecommon electrode layer 232. A liquid crystal composition according to anembodiment of the present invention can be used for liquid crystalelements with a variety of structures and liquid crystal display deviceswith a variety of display modes.

The distance between the pixel electrode layer 230 and the commonelectrode layer 232, which are adjacent to each other with the liquidcrystal composition 208 interposed therebetween, is a distance at whichliquid crystal in the liquid crystal composition 208 between the pixelelectrode layer 230 and the common electrode layer 232 responds to apredetermined voltage applied to each of the pixel electrode layer 230and the common electrode layer 232. The voltage applied is controlleddepending on the distance as appropriate.

The maximum thickness (film thickness) of the liquid crystal composition208 is preferably greater than or equal to 1 μm and less than or equalto 20 μm.

The liquid crystal composition 208 can be formed by a dispensing method(dropping method), or an injection method in which liquid crystal isinjected using capillary action or the like after the first substrate200 and the second substrate 201 are attached to each other.

Although not illustrated in FIGS. 1A and 1B, an optical film such as apolarizing plate, a retardation plate, or an anti-reflection film, orthe like is provided as appropriate. For example, circular polarizationwith the polarizing plate and the retardation plate may be used. Inaddition, a backlight or the like can be used as a light source.Alternatively, an optical film including the polymerizable monomercompound represented by the general formula (G1) in Embodiment 1 may beused.

In this specification, a substrate provided with a semiconductor element(e.g., a transistor), a pixel electrode layer, and a common electrodelayer is referred to as an element substrate (a first substrate), and asubstrate which faces the element substrate with a liquid crystalcomposition interposed therebetween is referred to as a countersubstrate (a second substrate).

As a liquid crystal display device according to an embodiment of thepresent invention, a transmissive liquid crystal display device in whichdisplay is performed by transmission of light from a light source, areflective liquid crystal display device in which display is performedby reflection of incident light, or a transflective liquid crystaldisplay device in which a transmissive type and a reflective type arecombined can be provided.

In the case of the transmissive liquid crystal display device, a pixelelectrode layer, a common electrode layer, a first substrate, a secondsubstrate, and other components such as an insulating film and aconductive film, which are provided in a pixel region through whichlight is transmitted, have a property of transmitting light in thevisible wavelength range. In the liquid crystal display device havingthe structure illustrated in FIG. 1A, it is preferable that the pixelelectrode layer and the common electrode layer have a light-transmittingproperty; however, if an opening pattern is provided, anon-light-transmitting material such as a metal film may be useddepending on the shape.

On the other hand, in the case of the reflective liquid crystal displaydevice, a reflective component which reflects light transmitted throughthe liquid crystal composition (e.g., a reflective film or substrate)may be provided on the side opposite to the viewing side of the liquidcrystal composition. Therefore, a substrate, an insulating film, and aconductive film which are provided between the viewing side and thereflective component and through which light is transmitted have alight-transmitting property with respect to light in the visiblewavelength range. Note that in this specification, a light-transmittingproperty refers to a property of transmitting at least light in thevisible wavelength range. In the liquid crystal display device havingthe structure illustrated in FIG. 1B, the pixel electrode layer or thecommon electrode layer on the side opposite to the viewing-side may havea light-reflecting property so that it can be used as a reflectivecomponent.

The pixel electrode layer 230 and the common electrode layer 232 may beformed with the use of one or more of the following: indium tin oxide(ITO), indium zinc; oxide obtained by mixing zinc oxide (ZnO) withindium oxide, a conductive material in which silicon oxide (SiO₂) ismixed into indium oxide, organoindium, organotin, indium oxidecontaining tungsten oxide, indium zinc oxide containing tungsten oxide,indium oxide containing titanium oxide, and indium tin oxide containingtitanium oxide; graphene; metals such as tungsten (W), molybdenum (Mo),zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta),chromium (Cr), cobalt (Co), nickel (NO, titanium (Ti), platinum (Pt),aluminum (Al), copper (Cu), and silver (Ag); alloys thereof; and metalnitrides thereof.

As the first substrate 200 and the second substrate 201, a glasssubstrate of barium borosilicate glass, aluminoborosilicate glass, orthe like, a quartz substrate, a plastic substrate, or the like can beused.

A liquid crystal composition including a polymerizable monomer compoundaccording to an embodiment of the present invention is applied to aliquid crystal element or a liquid crystal display device, whereby lowvoltage driving of the liquid crystal element or the liquid crystaldisplay device can be achieved. Thus, a reduction in power consumptionof the liquid crystal display device can be achieved.

Note that the structures, methods, and the like described in thisembodiment can be combined as appropriate with any of the structures,methods, and the like described in the other embodiments.

Embodiment 4

As a liquid crystal display device according to an embodiment of thepresent invention, a passive matrix liquid crystal display device and anactive matrix liquid crystal display device can be provided. In thisembodiment, an example of an active matrix liquid crystal display deviceaccording to an embodiment of the present invention will be describedwith reference to FIGS. 2A and 2B and FIGS. 3A to 3D.

FIG. 2A is a plan view of the liquid crystal display device andillustrates one pixel. FIG. 2B is a cross-sectional view taken alongline X1-X2 in FIG. 2A.

In FIG. 2A, a plurality of source wiring layers (including a wiringlayer 405 a) is arranged so as to be parallel to (extend in thelongitudinal direction in the drawing) and apart from each other. Aplurality of gate wiring layers (including a gate electrode layer 401)is arranged so as to be extended in the direction perpendicular to orsubstantially perpendicular to the source wiring layers (in thehorizontal direction in the drawing) and apart from each other. Commonwiring layers 408 are provided so as to be adjacent to the respectivegate wiring layers and extended in the direction parallel to orsubstantially parallel to the gate wiring layers, that is, in thedirection perpendicular to or substantially perpendicular to the sourcewiring layers (in the horizontal direction in the drawing). A roughlyrectangular space is surrounded by the source wiring layers, the commonwiring layer 408, and the gate wiring layer. In this space, a pixelelectrode layer and a common electrode layer of the liquid crystaldisplay device are provided. A transistor 420 for driving the pixelelectrode layer is provided at the upper left corner of the drawing. Aplurality of pixel electrode layers and a plurality of transistors arearranged in a matrix.

In the liquid crystal display device in FIGS. 2A and 2B, a firstelectrode layer 447 electrically connected to the transistor 420 servesas a pixel electrode layer, while a second electrode layer 446electrically connected to the common wiring layer 408 serves as a commonelectrode layer. Note that a capacitor is formed by the first electrodelayer and the common wiring layer. Although the common electrode layercan operate in a floating state (electrically isolated state), thepotential of the common electrode layer may be set to a fixed potential,preferably to a potential around an intermediate potential of an imagesignal which is transmitted as data at such a level as not to generateflickers.

A method can be used in which the gray scale is controlled by generatingan electric field parallel to or substantially parallel to a substrate(i.e., in the lateral direction) to move liquid crystal molecules in aplane parallel to the substrate. For such a method, an electrodestructure used in an IPS mode illustrated in FIGS. 2A and 2B and FIGS.3A to 3D can be employed.

In a lateral electric field mode such as an IPS mode, a first electrodelayer (e.g., a pixel electrode layer with which a voltage is controlledin each pixel) and a second electrode layer (e.g., a common electrodelayer with which a common voltage is applied to all pixels), each ofwhich has an opening pattern, are located below a liquid crystalcomposition. Therefore, the first electrode layer 447 and the secondelectrode layer 446, one of which is a pixel electrode layer and theother of which is a common electrode layer, are formed over a firstsubstrate 441, and at least one of the first electrode layer and thesecond electrode layer is formed over an interlayer film. The firstelectrode layer 447 and the second electrode layer 446 have not a flatshape but various opening patterns including, a bent portion or abranched comb-like portion. The first electrode layer 447 and the secondelectrode layer 446 have the same shape and do not overlap with eachother in order to generate an electric field between the electrodes.

The first electrode layer 447 and the second electrode layer 446 mayhave an electrode structure used in an FFS mode. In a lateral electricfield mode such as an FFS mode, a first electrode layer (e.g., a pixelelectrode layer with which a voltage is controlled in each pixel) havingan opening pattern is located below a liquid crystal composition, andfurther, a second electrode layer (e.g., a common electrode layer withwhich a common voltage is applied to all pixels) having a flat shape islocated below the opening pattern. In this case, the first electrodelayer and the second electrode layer, one of which is a pixel electrodelayer and the other of which is a common electrode layer, are formedover the first substrate 441, and the pixel electrode layer and thecommon electrode layer are stacked with an insulating film (or aninterlayer insulating film) interposed therebetween. One of the pixelelectrode layer and the common electrode layer is formed below theinsulating film (or the interlayer insulating film), whereas the otheris formed above the insulating film (or the interlayer insulating filth)and has various opening patterns including a bent portion or a branchedcomb-like portion. The first electrode layer 447 and the secondelectrode layer 446 have the same shape and do not overlap with eachother in order to generate an electric field between the electrodes.

The liquid crystal composition including the polymerizable monomerrepresented by the general formula (G1) described in Embodiment 1 isused as a liquid crystal composition 444. The liquid crystal composition444 may further contain an organic resin. In this embodiment, the liquidcrystal composition capable of exhibiting a blue phase and described inEmbodiment 2 is used as the liquid crystal composition 444. The liquidcrystal composition 444 is provided in a liquid crystal display devicewith a blue phase exhibited (with a blue phase shown) by being subjectedto polymer stabilization treatment.

With an electric, field generated between the first electrode layer 447as the pixel electrode layer and the second electrode layer 446 as thecommon electrode layer, liquid crystal of the liquid crystal composition444 is controlled. An electric field in the lateral direction is formedin the liquid crystal, so that liquid crystal molecules can becontrolled using the electric field. Since the liquid crystal moleculesaligned to exhibit a blue phase can be controlled in the directionparallel to the substrate, a wide viewing angle is obtained.

FIGS. 3A to 3B illustrate other examples of the first electrode layer447 and the second electrode layer 446. As illustrated in top views ofFIGS. 3A to 3D, first electrode layers 447 a to 447 d and secondelectrode layers 446 a to 446 d are arranged alternately. In FIG. 3A,the first electrode layer 447 a and the second electrode layer 446 ahave wavelike shapes with curves. In FIG. 3B, the first electrode layer447 b and the second electrode layer 446 b have shapes with concentriccircular openings. In FIG. 3C, the first electrode layer 447 c and thesecond electrode layer 446 c have comb-like shapes and partially overlapwith each other. In FIG. 3D, the first electrode layer 447 d and thesecond electrode layer 446 d have comb-like shapes in which theelectrode layers are engaged with each other. In the case where thefirst electrode layers 447 a, 447 b, and 447 c overlap with the secondelectrode layers 446 a, 446 b, and 446 c, respectively, as illustratedin FIGS. 3A to 3C, an insulating film is formed between the firstelectrode layer 447 and the second electrode layer 446 so that the firstelectrode layer 447 and the second electrode layer 446 are formed overdifferent films.

Since the first electrode layer 447 and the second electrode layer 446have opening patterns, they are illustrated as divided plural electrodelayers in the cross-sectional view in FIG. 2B. The same applies to theother drawings of this specification.

The transistor 420 is an inverted staggered thin film transistor inwhich the gate electrode layer 401, a gate insulating layer 402, asemiconductor layer 403, and wiring layers 405 a and 405 b whichfunction as a source electrode layer and a drain electrode layer areformed over the first substrate 441 having an insulating surface.

There is no particular limitation, on the structure of a transistorwhich can be used for a liquid crystal display device disclosed in thisspecification. For example, a staggered type or a planar type having atop-gate structure or a bottom-gate structure can be employed. Thetransistor may have a single-gate structure in which one channelformation region is formed, a double-gate structure in which two channelformation regions are formed, or a triple-gate structure in which threechannel formation regions are formed. Alternatively, the transistor mayhave a dual-gate structure including two gate electrode layerspositioned over and below a channel region with a gate insulating layerinterposed therebetween.

An insulating film 407 which is in contact with the semiconductor layer403, and an insulating film 409 are provided to cover the transistor420. An interlayer film 413 is stacked over the insulating film 409.

There is no particular limitation on the method for forming theinterlayer film 413, and the following method can be employed dependingon the material: spin coating, dip coating, spray coating, a dropletdischarging method (such as an ink-jet method), a printing method (suchas screen printing or offset printing), roll coating, curtain coating,knife coating, or the like.

The first substrate 441 and a second substrate 442 which is a countersubstrate are firmly attached to each other with a sealant with theliquid crystal composition 444 interposed therebetween. The liquidcrystal composition 444 can be formed by a dispensing method (a droppingmethod), or an injection method in which liquid crystal is injectedusing capillary action or the like after the first substrate 441 isattached to the second substrate 442.

As the sealant, typically, a visible light curable resin, a UV curableresin, or a thermosetting resin is preferably used. Typically, anacrylic resin, an epoxy resin, an amine resin, or the like can be used.Further, a photopolymerization initiator (typically, a UV polymerizationinitiator), a thermosetting agent, a filler, or a coupling agent may becontained in the sealant.

In this embodiment, since polymer stabilization treatment by lightirradiation is performed for forming the liquid crystal composition 444,a liquid crystal composition to which a photopolymerization initiator isadded is used as a liquid crystal composition including thepolymerizable monomer compound represented by the general formula (G1)in Embodiment 1 and exhibiting a blue phase.

After the space between the first substrate 441 and the second substrate442 is filled with the liquid crystal composition stabilizationtreatment is performed by light irradiation, whereby the liquid crystalcomposition 444 is formed. The light has a wavelength at which thephotopolymerizable monomer and the photopolymerization initiator whichare used for the liquid crystal composition 444 react. By such polymerstabilization treatment by light irradiation, the temperature rangewhere the liquid crystal composition 444 exhibits a blue phase can bebroadened.

Note that among the polymerizable monomer compounds represented by thegeneral formula (G1), use of a polymerizable monomer compound in which nand m are individually an even number from 2 to 20 is preferred becausepolymerization reaction is facilitated at the polymer stabilizationtreatment.

In the case where a photocurable resin such as a UV curable resin isused as a sealant and a liquid crystal composition is formed by adropping method, for example, the sealant may be cured in the lightirradiation step of the polymer stabilization treatment.

In this embodiment, a polarizing plate 443 a is provided on the outerside (on the side opposite to the liquid crystal composition 444) of thefirst substrate 441, and a polarizing plate 443 b is provided on theouter side (on the side opposite to the liquid crystal composition 444)of the second substrate 442. In addition to the polarizing plate, anoptical film such as a retardation plate or an anti-reflection film maybe provided. For example, circular polarization with the polarizingplate and the retardation plate may be used. Alternatively, an opticalfilm including the polymerizable monomer compound represented by thegeneral formula (G1) in Embodiment 1 may be used. Through the aboveprocess, a liquid crystal display device can be completed.

In the case of manufacturing a plurality of liquid crystal displaydevices using a large-sized substrate (a so-called multiple panelmethod), a division step can be performed before performing the polymerstabilization treatment or before providing the polarizing plates. Inconsideration of the influence of the division step on the liquidcrystal composition (such as alignment disorder due to force applied inthe division step), it is preferable that the division step be performedafter attaching the first substrate and the second substrate and beforeperforming the polymer stabilization treatment.

Although not illustrated, a backlight, a sidelight, or the like may beused as a light source. Light from the light source is emitted from theside of the first substrate 441 which is an element substrate so as topass through the second substrate 442 on the viewing side.

The first electrode layer 447 and the second electrode layer 446 can beformed using a light-transmitting conductive material such as indiumoxide containing tungsten oxide, indium zinc oxide containing tungstenoxide, indium oxide containing titanium oxide, indium tin oxidecontaining titanium oxide, ITO, indium zinc oxide, indium tin oxide towhich silicon oxide is added, or graphene.

The first electrode layer 447 and the second electrode layer 446 can beformed of one or more materials selected from metals such as tungsten(W), molybdenum (Mo), zirconium (Zr), hafnium (Hf), vanadium (V),niobium (Nb), tantalum (Ta), chromium (Cr), cobalt (Co), nickel (Ni),titanium (Ti), platinum (Pt), aluminum (Al), copper (Cu), and silver(Ag); alloys thereof; and metal nitrides thereof.

The first electrode layer 447 and the second electrode layer 446 can beformed using a conductive composition including a conductivemacromolecule (also referred to as a conductive polymer).

As the conductive high molecule, a so-called π-electron conjugatedconductive polymer can be used. Examples thereof include polyaniline ora derivative thereof, polypyrrole or a derivative thereof, polythiopheneor a derivative thereof, a copolymer of two or more kinds of aniline,pyrrole, and thiophene or a derivative thereof.

An insulating film serving as a base film may be provided between thefirst substrate 441 and the gate electrode layer 401. The base film hasa function of preventing diffusion of an impurity element from the firstsubstrate 441, and can be formed to have a single-layer structure or alayered structure using one or more of a silicon nitride film, a siliconoxide film, a silicon nitride oxide film, and a silicon oxynitride film.The gate electrode layer 401 can be formed with the use of any of metalmaterials such as molybdenum, titanium, chromium, tantalum, tungsten,aluminum, copper, neodymium, and scandium, and an alloy material whichcontains any of these materials as its main component. Alternatively, asemiconductor film typified by a polycrystalline silicon film doped withan impurity element such as phosphorus, or a silicide film such as anickel silicide film may be used as the gate electrode layer 401. Thegate electrode layer 401 may have a single-layer structure or layeredstructure. By using a light-blocking conductive film as the gateelectrode layer 401, light from a backlight (light emitted through thefirst substrate 441) can be prevented from entering the semiconductorlayer 403.

For example, as a two-layer structure of the gate electrode layer 401,the following structures are preferable: a two-layer structure of analuminum layer and a molybdenum layer stacked thereover, a two-layerstructure of a copper layer and a molybdenum layer stacked thereover, atwo-layer structure of a copper layer and a titanium nitride layer or atantalum nitride layer stacked thereover, and a two-layer structure of atitanium nitride layer and a molybdenum layer. As a three-layerstructure, a layered structure in which a tungsten layer or a tungstennitride layer, an alloy layer of aluminum and silicon or an alloy layerof aluminum and titanium, and a titanium nitride layer or a titaniumlayer are stacked is preferable.

For example, the gate insulating layer 402 can be formed by a plasma CVDmethod, or a sputtering method, with the use of a silicon oxide film, agallium oxide film, an aluminum oxide film, a silicon nitride film, asilicon oxynitride film, an aluminum, oxynitride film, or a siliconnitride oxide film. Alternatively, a high-k material such as hafniumoxide, yttrium oxide, lanthanum oxide, hafnium silicate (HfSi_(x)O_(y)(x>0, y>0)), hafnium aluminate (HfAl_(x)O_(y) (x>0, y>0)), hafniumsilicate to which nitrogen is added, or hafnium aluminate to whichnitrogen is added may be used as a material for the gate insulatinglayer 402. The use of such a high-k material enables a reduction in gateleakage current.

Alternatively, the gate insulating layer 402 can be formed using asilicon oxide layer by a CVD method using an organosilane gas. As anorganosilane gas, a silicon-containing compound such astetraethoxysilane (TEOS) (chemical formula: Si(OC₂H₅)₄),tetramethylsilane (TMS) (chemical formula: Si(CH₃)₄),tetramethylcyclotetrasiloxane (TMCTS), octamethylcyclotetrasiloxane(OMCTS), hexamethyldisilazane (HMDS), triethoxysilane (SiH(OC₂H₅)₃), ortrisdimethylaminosilane (SiH(N(CH₃)₂)₃) can be used. Note that the gateinsulating layer 402 may have a s single layer structure or a stackedstructure.

A material of the semiconductor layer 403 is not particularly limitedand may be determined as appropriate depending on characteristics neededfor the transistor 420. Examples of a material which can be used for thesemiconductor layer 403 will be described.

The semiconductor layer 403 can be formed using the following material:an amorphous semiconductor formed by a chemical vapor deposition methodusing a semiconductor source gas typified by silane or germane or by aphysical vapor deposition method such as sputtering; a polycrystallinesemiconductor formed by crystallizing the amorphous semiconductor withthe use of light energy or thermal energy; a microcrystallinesemiconductor in which a minute crystalline phase and an amorphous phasecoexist; or the like. The semiconductor layer can be formed by asputtering method, an LPCVD method, a plasma CVD method, or the like.

A typical example of an amorphous semiconductor is hydrogenatedamorphous silicon, while a typical example of a crystallinesemiconductor is polysilicon. Examples of polysilicon (polycrystallinesilicon) are as follows: so-called high-temperature polysilicon whichcontains polysilicon formed at a process temperature of 800° C. orhigher as its main component, so-called low-temperature polysiliconwhich contains polysilicon formed at a process temperature of 600° C. orlower as its main component, and polysilicon obtained by crystallizingamorphous silicon with the use of an element that promotescrystallization, or the like. It is needless to say that amicrocrystalline semiconductor or a semiconductor partly containing acrystal phase can be used as described above.

Alternatively, the semiconductor layer 403 may be formed with the use ofan oxide semiconductor. For example, a metal oxide material containingtwo or more elements selected from In, Ga, Zn, and Sn may be used as theoxide semiconductor; A four-component metal oxide such as anIn—Sn—Ga—Zn—O-based material; a three-component metal oxide such as anIn—Ga—Zn—O-based material, an In—Sn—Zn—O-based material, anIn—Al—Zn—O-based material, a Sn—Ga—Zn—O-based material, anAl—Ga—Zn—O-based material, a Sn—Al—Zn—O-based material, or aHf—In—Zn—O-based material; a two-component metal oxide such as anIn—Zn—O-based material, a Sn—Zn—O-based material, an Al—Zn—O-basedmaterial, a Zn—Mg—O-based material, a Sn—Mg—O-based material, anIn—Mg—O-based material, or an In—Ga—O-based material; or asingle-component metal oxide such as an In—O-based material, aSn—O-based material, or a Zn—O-based material may be used. In addition,any of the above oxide semiconductors may contain an element other thanIn, Ga, Sn, and Zn, for example, SiO₂.

Here, for example, the In—Ga—Zn-based oxide semiconductor refers to anoxide semiconductor containing indium (In), gallium (Ga), and zinc (Zn)and there is no particular limitation on the composition ratio thereof.

For the oxide semiconductor layer, a thin film expressed by the chemicalformula, InMO₃(ZnO)_(m) (m>0), can be used. Here, m represents one ormore metal elements selected from Zn, Ga, Al, Mn, and Co. For example, mcan be Ga, Ga and Al, Ga and Mn, or Ga and Co.

In the case where the In—Sn—Zn—O-based material is used as oxidesemiconductor, a target May have a composition ratio of In:Sn:Zn=1:2:2,In:Sn:Zn=2:1:3; In:Sn:Zn=1:1:1, for example.

In the case where an In—Zn—O-based material is used as an oxidesemiconductor, a target to be used has a composition ratio of In:Zn=50:1to 1:2 in an atomic ratio (In₂O₃:ZnO=25:1 to 1:4 in a molar ratio),preferably In:Zn=20:1 to 1:1 in an atomic ratio (In₂O₃:ZnO=10:1 to 1:2in a molar ratio), further preferably In:Zn=15:1 to 1.5:1 in an atomicratio (In₂O₃:ZnO=15:2 to 3:4 in a molar ratio). For example, in a targetused for formation of an In—Zn—O-based oxide semiconductor which has anatomic ratio of In:Zn:O═X:Y:Z, the relation of Z>1.5X+Y is satisfied.

As the oxide semiconductor layer, a CAAC-OS (c-axis aligned crystallineoxide semiconductor) film which is neither completely single crystal norcompletely amorphous can be used. The CAAC-OS film is an oxidesemiconductor layer with a crystal-amorphous mixed phase structure wherecrystal parts and amorphous parts are included in an amorphous phase. Inthe crystal portion included in the CAAC-OS film, c-axes are aligned inthe direction parallel (including the range of −5° to 5°) to a normalvector of the surface where the CAAC-OS film is formed or a normalvector of the surface of the CAAC-OS film, a triangular or hexagonalatomic arrangement is provided when seen from the directionperpendicular to an a-b plane, and metal atoms are arranged in a layeredmanner or metal atoms and oxygen atoms are arranged in a layered mannerwhen seen from the direction perpendicular (including the range of 85°to 95°) to the c-axis. Note that among crystal parts, the directions ofan a-axis and a b-axis of one crystal part may be different from thoseof another crystal part.

In a process of forming the semiconductor layer and the wiring layer, anetching step is used to process thin films into desired shapes. Dryetching or wet etching can be employed for the etching step.

The etching conditions (such as an etchant, etching time, andtemperature) are appropriately adjusted depending on the material sothat the material can be etched to have a desired shape.

As a material of the wiring layers 405 a and 405 b serving as source anddrain electrode layers, an element selected from Al, Cr, Ta, Ti, Mo, andW; an alloy containing any of the above elements as its component; analloy film containing a combination of any of these elements; and thelike can be given. Further, in the case where heat treatment isperformed, the conductive film preferably has heat resistance againstthe heat treatment. Since the use of aluminum alone brings disadvantagessuch as low heat resistance and a tendency to corrosion, aluminum isused in combination with a conductive material having heat resistance.As the conductive material having heat resistance which is combined withaluminum, it is possible to use an element selected from titanium (Ti),tantalum (Ta), tungsten (W), molybdenum (Mo), chromium (Cr), neodymium(Nd), and scandium (Sc); an alloy containing any of these elements asits component; an alloy containing a combination of any of theseelements; or a nitride containing any of these elements as itscomponent.

The gate insulating layer 402, the semiconductor layer 403, and thewiring layers 405 a and 405 b serving as source and drain electrodelayers may be successively formed without being exposed to the air.Successive film formation without exposure to the air makes it possibleto obtain each interface between stacked layers, which is notcontaminated by atmospheric components or impurity elements floating inthe air. Therefore, variation in characteristics of the transistor canbe reduced.

Note that the semiconductor layer 403 is partly etched so as to have agroove (a depressed portion).

As the insulating film 407 and the insulating film 409 which cover thetransistor 420, an inorganic insulating film or an organic insulatingfilm formed by a dry method or a wet method can be used. For example, itis possible to use a silicon nitride filth, a silicon oxide film, asilicon oxynitride film, an aluminum oxide film, or a tantalum oxidefilth, which is formed by a CVD method, a sputtering method, or thelike. Alternatively, an organic material such as polyimide, acrylic, abenzocyclobutene-based resin, polyamide, epoxy can be used. As, analternative to such organic materials, it is possible to use alow-dielectric constant material (a low-k material), a siloxane-basedresin, phosphosilicate glass (PSG), borophosphosilicate glass (BPSG), orthe like. A gallium oxide film can also be used as the insulating film407.

Note that the siloxane-based resin corresponds to a resin including aSi—O—Si bond formed using a siloxane-based material as a startingmaterial. The siloxane-based resin may include as a substituent anorganic group (e.g., an alkyl group or an aryl group) or a fluoro group.The organic group may include a fluoro group. A siloxane-based resin isapplied by a coating method and baked; thus, the insulating film 407 canbe formed.

Alternatively, the insulating film 407 and the insulating film 409 maybe formed by stacking a plurality of insulating films formed using anyof these materials. For example, a structure may be employed in which anorganic resin film is stacked over an inorganic insulating film.

Further, with the use of a resist mask having regions with pluralthicknesses (typically, two different thicknesses) which is formed usinga multi-tone mask, the number of photomasks can be reduced, resulting ina simplified process and lower cost.

As described above, a liquid crystal composition including thepolymerizable monomer compound represented by the general formula (G1)is applied to a liquid crystal display device, whereby a liquid crystaldisplay device capable of low voltage driving can be provided. Thus, areduction in power consumption of the liquid crystal display device canbe achieved.

Since the liquid crystal composition including the polymerizable monomercompound represented by the general formula (G1) and exhibiting a bluephase is capable of quick response, a high-performance liquid crystaldisplay device can be achieved.

Note that the structures, methods, and the like described in thisembodiment can be combined as appropriate with any of the structures,methods, and the like described in the other embodiments.

Embodiment 5

In this embodiment, a liquid crystal display device including the liquidcrystal composition described in the above embodiments will bedescribed. The liquid crystal display device includes a transistor in apixel portion, and further in a driver circuit. Further, part or thewhole of the driver circuit can be formed over the same substrate as thepixel portion, using the transistor, whereby a system-on-panel can beobtained.

The liquid crystal display device includes a liquid crystal element(also referred to as a liquid crystal display element) as a displayelement.

Further, a liquid crystal display device includes a panel in which aliquid crystal display element is sealed, and a module in which an IC orthe like including a controller is mounted to the panel. An embodimentof the present invention also relates to an element substrate, whichcorresponds to one mode in which the display, element has not beencompleted in a manufacturing process of the liquid crystal displaydevice, and the element substrate is provided with a means for supplyingcurrent to the display element in each of a plurality of pixels.Specifically, the element substrate may be in a state where it isprovided only with a pixel electrode of the display element, in a statewhere a conductive film to be a pixel electrode has been formed and theconductive film has not yet been etched to form the pixel electrode, orin any other state.

The appearance and a cross section of a liquid, crystal display panel,which is an embodiment of a liquid crystal display device, will bedescribed with reference to FIGS. 4A1, 4A2, and 4B. FIGS. 4A1 and 4A2are each a top view of a panel in which transistors 4010 and 4011 formedover a first substrate 4001 and a liquid crystal element 4013 are sealedbetween the first substrate 4001 and a second substrate 4006 with asealant 4005. FIG. 4B is a cross-sectional view taken along line M-N ofFIGS. 4A1 and 4A2.

The sealant 4005 is provided to surround a pixel portion 4002 and ascanning line driver circuit 4004 that are provided over the firstsubstrate 4001. The second substrate 4006 is provided over the pixelportion 4002 and the scanning line driver circuit 4004. Therefore, thepixel portion 4002 and the scanning line driver circuit 4004 are sealedtogether with a liquid crystal composition 4008, by the first substrate4001, the sealant 4005, and the second substrate 4006.

In FIG. 4A1, a signal line driver circuit 4003 that is formed using asingle crystal semiconductor film or a polycrystalline semiconductorfilm over a substrate separately prepared is mounted in a regiondifferent from the region surrounded by the sealant 4005 over the firstsubstrate 4001. Note that FIG. 4A2 illustrates an example in which partof the signal line driver circuit is formed using a transistor providedover the first substrate 4001. A signal line driver circuit 4003 b isformed over the first substrate 4001, and a signal line driver circuit4003 a formed using a single crystal semiconductor film or apolycrystalline semiconductor film is mounted on a substrate separatelyprepared.

Note that there is no particular limitation on the connection method ofa driver circuit which is separately formed, and COG, wire bonding, TAB,or the like can be used. FIG. 4A1 illustrates an example of mounting thesignal line driver circuit 4003 by COG, and FIG. 4A2 illustrates anexample of mounting the signal line driver circuit 4003 by TAB.

The pixel portion 4002 and the scanning line driver circuit 4004provided over the first substrate 4001 each include a plurality oftransistors. FIG. 4B illustrates the transistor 4010 included in thepixel portion 4002 and the transistor 4011 included in the scanning linedriver circuit 4004. An insulating layer 4020 and an interlayer film4021 are provided over the transistors 4010 and 4011.

As the transistors 4010 and 4011, the transistor which is described inEmbodiment 4 can be employed.

Further, a conductive layer may be provided over the interlayer film4021 or the insulating layer 4020 so as to overlap with a channelformation region of a semiconductor layer of the transistor 4011 for thedriver circuit. The conductive layer may have the same potential as or apotential different from that of a gate electrode layer of thetransistor 4011 and can function as a second gate electrode layer.Further, the potential of the conductive layer may be GND or 0 V, or theconductive layer may be in a floating state.

A pixel electrode layer 4030 and a common electrode layer 4031 areprovided over the interlayer film 4021, and the pixel electrode layer4030 is electrically connected to the transistor 4010. The liquidcrystal element 4013 includes the pixel electrode layer 4030, the commonelectrode layer 4031, and the liquid crystal composition 4008. Note thata polarizing plate 4032 a and a polarizing plate 4032 b are provided onthe outer sides of the first substrate 4001 and the second substrate4006, respectively.

The liquid crystal composition including the polymerizable monomercompound represented by the general formula (G1) described in Embodiment1 is used as the liquid crystal composition 4008. The structures of thepixel electrode layer and the common electrode layer described in theabove embodiment can be used for the pixel electrode layer 4030 and thecommon electrode layer 4031.

In this embodiment, the liquid crystal composition including thepolymerizable monomer compound represented, by the general formula (G1)and exhibiting a blue phase is used as the liquid crystal composition4008. The liquid crystal composition 4008 is provided in a liquidcrystal display device with a blue phase exhibited (with a blue phaseshown) by being subjected to polymer stabilization treatment. Therefore,in this embodiment, the pixel electrode layer 4030 and the commonelectrode layer 4031 have opening patterns, as the electrode layersillustrated in FIG. 1A or FIGS. 3A to 3D.

With an electric field generated between the pixel electrode layer 4030and the common electrode layer 4031, liquid crystal of the liquidcrystal composition 4008 is controlled. An electric field in a lateraldirection is formed in the liquid crystal, so that liquid crystalmolecules can be controlled using the electric field. Since the liquidcrystal molecules aligned to exhibit a blue phase can be controlled inthe direction parallel to the substrate, a wide viewing angle isobtained.

Among the polymerizable monomer compounds represented by the generalformula (G1), use of a polymerizable monomer compound in which n and mare individually an even number from 2 to 20 is preferred becausepolymerization reaction is facilitated at the polymer stabilizationtreatment.

As the first substrate 4001 and the second substrate 4006, glass,plastic, or the like having a light-transmitting property can be used.As plastic, a fiberglass-reinforced plastics (FRP) plate, a polyvinylfluoride (PVF) film, a polyester film, or an acrylic resin film can beused. A sheet with a structure in which an aluminum foil is sandwichedbetween PVF films or polyester films can also be used.

A columnar spacer denoted by reference numeral 4035 is obtained byselective etching, of an insulating film and is provided in order tocontrol the thickness of the liquid crystal composition 4008 (a cellgap). Alternatively, a spherical spacer may be used. In the liquidcrystal display device including the liquid crystal composition 4008,the cell gap which is the thickness of the liquid crystal composition ispreferably greater than or equal to 1 μm and less than or equal to 20μm. In this specification, the thickness of a cell gap refers to themaximum thickness (film thickness) of a liquid crystal composition.

Although FIGS. 4A1, 4A2, and 4B illustrate examples of transmissiveliquid crystal display devices, an embodiment of the present inventioncan also be applied to a transflective liquid crystal display device anda reflective liquid crystal display device.

FIGS. 4A1, 4A2, and 4B illustrate examples of liquid crystal displaydevices in which a polarizing plate is provided on the outer side theviewing side) of a substrate; however, the polarizing plate may beprovided on the inner hide of the substrate. The position of thepolarizing plate may be determined as appropriate depending on thematerial of the polarizing plate and conditions of the manufacturingprocess. Furthermore, a light-blocking layer serving as a black matrixmay be provided.

A color filter layer or a light-blocking layer may be formed as part ofthe interlayer film 4021. In FIGS. 4A1, 4A2, and 4B, a light-blockinglayer 4034 is provided on the second substrate 4006 side so as to coverthe transistors 4010 and 4011. By providing the light-blocking layer4034, the contrast can be more increased and the transistors can be morestabilized.

The transistors may be, but is not necessarily, covered with theinsulating layer 4020 which functions as a protective film of thetransistors.

Note that the protective film is provided to prevent entry ofcontaminant impurities such as an organic substance, metal, and,moisture in the air and is preferably a dense film. The protective filmmay be formed by a sputtering method to have a single-layer structure ora layered structure including any of a silicon oxide film, a siliconnitride film, a silicon oxynitride film, a silicon nitride oxide film,an aluminum oxide film, an aluminum nitride film, an aluminum oxynitridefilm, and an aluminum nitride oxide film.

Further, in the case of further forming a light-transmitting insulatinglayer as a planarizing insulating film, the light-transmittinginsulating layer can be formed using an organic material having heatresistance, such as polyimide, acrylic; a benzocyclobutene-based resin,polyamide, or epoxy. As an alternative to such organic materials, it ispossible to use a low-dielectric constant material (a low-k material), asiloxane-based resin, phosphosilicate glass (PSG), borophosphosilicateglass (BPSG), or the like. The insulating layer may be formed bystacking a plurality of insulating films formed of these materials.

There is no particular limitation on the method for forming theinsulating layer having a stacked structure, and the following methodcan be employed depending on the material: sputtering, spin coating, dipcoating, spray coating, a droplet discharging method (such as an ink-jetmethod), a printing method (such as screen printing or offset printing),roll coating, curtain coating, knife coating, or the like.

The pixel electrode layer 4030 and the common electrode layer 4031 canbe formed using a light-transmitting conductive material such as indiumoxide containing tungsten oxide, indium zinc oxide containing tungstenoxide, indium oxide containing titanium oxide, indium tin oxidecontaining titanium oxide, ITO, indium zinc oxide, indium tin oxide towhich silicon oxide is added, or graphene.

Alternatively, the pixel electrode layer 4030 and the common electrodelayer 4031 can be formed using one or more of the following: metals suchas tungsten (W), molybdenum (Mo), zirconium (Zr), hafnium (Hf), vanadium(V), niobium (Nb), tantalum (Ta), chromium (Cr), cobalt (Co), nickel(Ni), titanium (Ti), platinum (Pt), aluminum (Al), copper (Cu), andsilver (Ag); alloys thereof; and nitrides thereof.

The pixel electrode layer 4030 and the common electrode layer 4031 canbe formed using a conductive composition including a conductivemacromolecule (also referred to as a conductive polymer).

Further, a variety of signals and potentials are supplied to the signalline driver circuit 4003 which is formed separately, the scanning linedriver circuit 4004, or the pixel portion 4002 from an FPC 4018.

Further, since the transistor is easily broken by static electricity orthe like, a protective circuit for protecting the driver circuits ispreferably provided over the same substrate as a gate line or a sourceline. The protection circuit is preferably formed using a nonlinearelement.

In FIGS. 4A1, 4A2, and 4B, a connection terminal electrode 4015 isformed using the same conductive film as the pixel electrode layer 4030,and a terminal electrode 4016 is formed using the same conductive filmas source electrode layers and drain electrode layers of the transistors4010 and 4011.

The connection terminal electrode 4015 is electrically connected to aterminal included in the FPC 4018 through an anisotropic conductive film4019.

Although FIGS. 4A1, 4A2, and 4B illustrate an example in which thesignal line driver circuit 4003 is formed separately and mounted on thefirst substrate 4001, an embodiment of the present invention is notlimited to this structure. The scanning line driver circuit may beSeparately formed and then mounted, or only part of the signal linedriver circuit or part of the scanning line driver circuit may beseparately formed and then mounted.

As described above, a liquid crystal composition including thepolymerizable monomer compound represented by the general formula (G1)is applied to a liquid crystal display device, whereby a liquid crystaldisplay device capable of low voltage driving can be provided. Thus, areduction in power consumption of the liquid crystal display device canbe achieved.

Since the liquid crystal composition including the polymerizable monomercompound represented by the general formula (G1) and exhibiting a bluephase is capable of quick response, a high-performance liquid crystaldisplay device can be achieved.

Note that the structures, methods, and the like described in thisembodiment can be combined as appropriate with any of the structures,methods, and the like described in the other embodiments.

Embodiment 6

A liquid crystal display device disclosed in this specification can beapplied to a variety of electronic devices (including game machines).Examples of electronic devices are a television set (also referred to asa television or a television receiver), a monitor of a computer or thelike, a camera such as a digital camera or a digital video camera, adigital photo frame, a mobile phone handset (also referred, to as amobile phone or a mobile phone device), a portable game machine, aportable information terminal, an audio reproducing device, alarge-sized game machine such as a pachinko machine, and the like.

FIG. 5A illustrates a laptop personal computer, which includes a mainbody 3001, a housing 3002, a display portion 3003, a keyboard 3004, andthe like. The liquid crystal display device described in any of theabove embodiments is used for the display portion 3003, whereby lowvoltage driving and a reduction in power consumption of the laptoppersonal computer can achieved.

FIG. 5B illustrates a personal digital assistant (PDA), which includes amain body 3021 provided with a display portion 3023, an externalinterface 3025, operation buttons 3024, and the like. A stylus 3022 isprovided as an accessory for operation. The liquid crystal displaydevice described in any of the above embodiments is used for the displayportion 3023, whereby low voltage driving and a reduction in powerconsumption of the personal digital assistant (PDA) can be achieved.

FIG. 50 illustrates an e-book reader, which includes two housings, ahousing 2701 and a housing 2703. The housing 2701 and the housing 2703are combined with a hinge 2711 so that the e-book reader can be openedand closed with the hinge 2711 as an axis. With such a structure, thee-book reader can operate like a paper book.

A display portion 2765 and a display portion 2707 are incorporated inthe housing 2701 and the housing 2703, respectively. The display portion2705 and the display portion 2707 may display one image or differentimages. In the structure where different images are, displayed in theabove display portions, for example, the right display portion (thedisplay portion 2705 in FIG. 5C) can display text and the tell displayportion (the display portion 2707 in FIG. 5C) can display images. Theliquid crystal display device described in any of the above embodimentsis used for the display portions 2705 and 2707, whereby low voltagedriving and a reduction in power consumption of the e-book reader can beachieved. In the case of using a transflective or reflective liquidcrystal display device as the display portion 2705, the e-book readermay be used in a comparatively bright environment; therefore, a solarcell may be provided so that power generation by the solar cell andcharge by a battery can be performed. When a lithium ion battery is usedas the battery, there are advantages of downsizing and the like.

FIG. 5C illustrates an example in which the housing 2701 is providedwith an operation portion and the like. For example, the housing 2701 isprovided with a power switch 2721, operation keys 2723, a speaker 2725,and the like. With the operation keys 2723, pages can be turned. Notethat a keyboard, a pointing device, or the like may also be provided onthe surface of the housing, on which the display portion is provided.Furthermore, an external connection terminal (an earphone terminal, aUSB terminal, or the like), a recording medium insertion portion, andthe like may be provided on the back surface or the side surface of thehousing. Further, the e-book reader may have a function of an electronicdictionary.

The e-book reader may transmit and receive data wirelessly. Throughwireless communication, desired book data or the like can be purchasedand downloaded from an electronic book server.

FIG. 5D illustrates a mobile phone, which includes two housings, ahousing 2800 and a housing 2801. The housing 2801 includes a displaypanel 2802, a speaker 2803, a microphone 2804, a pointing device 2806, acamera lens 2807, an external connection terminal 2808, and the like. Inaddition, the housing 2800 includes a solar cell 2810 having a functionof charge of the mobile phone, an external memory slot 2811, and thelike. An antenna is incorporated in the housing 2801. The liquid crystaldisplay device described in any of the above embodiments is used for thedisplay panel 2802, whereby low voltage driving and a reduction in powerconsumption of the mobile phone can be achieved.

Further, the display panel 2802 is provided with a touch panel. Aplurality of operation keys 2805 which is displayed as, images isillustrated by dashed lines in FIG. 5D. Note that a boosting circuit bywhich a voltage output from the solar cell 2810 is increased to besufficiently high for each circuit is also provided.

The display direction of the display panel 2802 is changed asappropriate depending on a usage pattern. Further, the camera lens 2807is provided on the same surface as the display panel 2802, so that themobile phone can be used as a video phone. The speaker 2803 and themicrophone 2804 can be used for videophone calls, recording and playingsound, and the like as well as voice calls. Furthermore, the housings2800 and 2801 which are developed as illustrated in FIG. 5D can overlapwith each other by sliding; thus, the size of the mobile phone can bedecreased, which makes the mobile phone suitable for being carried.

The external connection terminal 2808 can be connected to an AC adapterand various types of cables such as a USB cable, and charging and datacommunication with a personal computer are possible. Moreover, a largeamount of data can be stored by inserting a storage medium into theexternal memory slot 2811 and can be moved.

Further, in addition to the above functions, an infrared communicationfunction, a television reception function, or the like may be provided.

FIG. 5E illustrates a digital video camera, which includes a main body3051, a display portion A 3057, an eyepiece 3053, an operation switch3054, a display portion B 3055, a battery 3056, and the like. The liquidcrystal display device described in any of the above embodiments is usedfor the display portion, A 3057 and the display portion B 3055, wherebylow voltage driving and a reduction in power consumption of the digitalvideo camera can be achieved.

FIG. 5F illustrates a television set, which includes a housing 9601, adisplay portion 9603, and the like. The display portion 9603 can displayimages. Here; the housing 9601 is supported by a stand 9605. The liquidcrystal display device described in any of the above embodiments is usedfor the display portion 9603, whereby low voltage driving and areduction in power consumption of the television set can be achieved.

The television set can operate with an operation switch of the housing9601 or a separate remote control device. Further, the remote controllermay be provided with a display portion for displaying data output fromthe remote controller.

Note that the television set is provided with a receiver, a modem, andthe like. With the use of the receiver; general television broadcastingcan be received. Moreover, when the display device is connected to acommunication network with or without wires via the modem, one-way (froma sender to a receiver) or two-way (between a sender and a receiver orbetween receivers) data communication can be performed.

Note that the structures, methods, and the like described in thisembodiment can be combined as appropriate with any of the structures,methods, and the like described in the other embodiments.

Example 1

In this example, an example of synthesizing1,4-bis-[4-(6-acryloyloxy-n-hexyl-1-oxy)-2-fluorobenzoyloxy]benzene(abbreviation: Dac-PEPEP-F-O6) represented by the structural formula(105) in Embodiment 1 will be described.

A synthesis scheme of1,4-bis-[4-(6-acryloyloxy-n-hexyl-1-oxy)-2-fluorobenzoyloxy]benzene,(abbreviation: Dac-PEPEP-F-O6) represented by the structural formula(105) is shown in (E1-1) below.

Into a 300-mL recovery flask were put 1.3 g (4.1 mmol) of4-(6-acryloyloxy-n-hexyl-1-oxy)-2-fluoro-benzoic acid, 0.18 g (1.7 mmol)of 1,4-benzenediol, 100 mL of acetone, and 50 mL of dichloromethane. Tothis mixture, 76 mg (0.62 mmol) of 4-dimethylaminopyridine was added andstirred in the air. To this solution, 0.79 g (4.1 mmol) of1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) wasadded, and stirred in the air at room temperature for 41 hours. Afterthat, completion of the reaction was confirmed using silica gel thinlayer chromatography (TLC).

The obtained solution was concentrated, and chloroform, a saturatedaqueous solution elf-sodium hydrogen carbonate, and saturated salinewere added, and then, the aqueous layer was extracted three times withchloroform. An organic layer and the extracted solution were mixed anddried with magnesium sulfate, and thus obtained mixture was gravityfiltered. The filtrate was condensed, and the obtained solid waspurified by silica gel column chromatography (developing solvent:chloroform). The obtained fraction was concentrated to give a whitesolid. The white solid was purified by high performance liquidchromatography (HPLC) to give 0.70 g of a white solid in a yield of 61%.

This compound was identified by a nuclear magnetic resonance (NMR) as1,4-bis-[4-(6-acryloyloxy-n-hexyl-1-oxy)-2-fluorobenzoyloxy]benzene(abbreviation: Dac-PEPEP-F-O6) which was a target substance. FIGS. 6A to6C are the ¹H NMR charts. Note that FIG. 6B is an enlarged chart showingthe range of 5.5 ppm to 8.5 ppm in FIG. 6A. Note also that FIG. 6C is anenlarged chart showing the range of 1.5 ppm to 4.5 ppm in FIG. 6A.

¹H NMR data of the obtained substance are as follows: ¹H NMR-(CDCl₃, 300MHz): δ (ppm)=1.47-1.51 (m, 8H), 1.68-1.87 (m, 8H), 4.03 (t, J=6.3 Hz,4H), 4.19 (t, J=6.6 Hz, 4H), 5.83 (dd, J1=10.5 Hz, J2=1.8 Hz, 2H), 6.13(dd, J1=10.5 Hz, J2=17.4 Hz, 2H), 6.41 (dd, J1=1.5 Hz, J2=17.1 Hz, 2H),6.69 (dd, J1=2.6 Hz, J2=12.8 Hz, 2H), 6.77 (dd, J1=2.4 Hz, J2=8.7 Hz,2H), 7.27 (s, 4H), 8.02-8.08 (m, 2H).

FIG. 7 shows the absorption spectrum of1,4-bis-[4-(6-acryloyloxy-n-hexyl-1-oxy)-2-fluorobenzoyloxy]benzene(abbreviation: Dac-PEPEP-F-O6) in a dichloromethane solution ofDac-PEPEP-F-O6. The absorption spectrum was measured with anultraviolet-visible spectrophotometer (V-550, manufactured by JASCOCorporation). The absorption spectrum in FIG. 7 was obtained bysubtracting the absorption spectrum of a quartz cell filled withdichloromethane from that of the quartz cell filled with thedichloromethane solution of Dac-PEPEP-F-O6. In FIG. 7, the horizontalaxis indicates wavelength (nm) and the vertical axis indicatesabsorption intensity (arbitrary unit). In the case of thedichloromethane solution, an absorption was observed at around 260 nm.

Example 2

In this example, the results of the characteristics evaluation on theliquid crystal element of Example 1 formed with the use of the liquidcrystal composition including the polymerizable monomer according to anembodiment of the present invention will be described.

Table 1 shows components of the liquid crystal composition used for theliquid crystal element manufactured in this example. In Table 1, themixture ratios are all represented in weight ratios.

TABLE 1 Name of components Ratio (wt %) Liquid Crystal 1 E-8 34.1 LiquidCrystal 2 CPP-3FF 25.4 Liquid Crystal 3 PEP-5CNF 25.4 Chiral AgentISO-(6OBA)₂ 6.9 Polymerizable DMeAc 4 Monomer Dac-PEPEP-F-O6 4Polymerization DMPAP 0.2 Initiator Total 100.0

In the liquid crystal element of this example; the following componentswere used: liquid crystal mixture E-8 (produced by LCC Corporation) asLiquid Crystal 1;4-(trans-4-n-propylcyclohexyl)-3′,4′-difluoro-1,1′-biphenyl(abbreviation: CPP-3FF) (produced by Daily Polymer Corporation) asLiquid Crystal 2; 4-n-pentylbenzoic acid 4-cyano-3-fluorophenyl(abbreviation: PEP-5CNF) (produced by Daily Polymer Corporation) asLiquid Crystal 3; 1,4:3,6-dianhydro-2,5-bis[4-(n-hexyl-1-oxy)benzoicacid]sorbitol (abbreviation: ISO-(6OBA)₂) (produced by Midori KagakuCo., Ltd.) as a chiral agent; dodecyl methacrylate: (abbreviation:DMeAc) (produced by Tokyo Chemical Industry Co., Ltd.) which is anon-liquid-crystalline UV-polymerizable monomer compound as apolymerizable monomer compound;1,4-bis-[4-(6-acryloyloxy-n-hexyl-1-oxy)-2-fluorobenzoyloxy]benzene(abbreviation: Dac-PEPEP-F-O6) produced in Example 1, which is a liquidcrystalline and UV-polymerizable monomer compound of an embodiment ofthe present invention as a polymerizable monomer compound; and DMPAP(abbreviation) (produced by Tokyo Chemical Industry Co., Ltd.) as apolymerization initiator.

The structural formulae of CPP-3FF (abbreviation) and PEP-5CNF(abbreviation) is the liquid crystal materials, ISO-(6OBA)₂(abbreviation) as the chiral agent; dodecyl methacrylate (DMeAc)(abbreviation) and Dac-PEPEP-F-O6 (abbreviation) as the polymerizableMonomer Compounds, and DMPAP (abbreviation) as the polymerizationinitiator, which were used in this example, are shown below.

The liquid crystal element of this example was manufactured in such amanner that a glass substrate over which a pixel electrode layer and acommon electrode layer were formed in comb-like shapes as in FIG. 3D anda glass substrate serving as a counter substrate were bonded to eachother using sealant with a space (4 μm) provided therebetween and then aliquid crystal composition obtained by mixing the components in Table 1stirred in an isotropic phase at ratios shown in Table 1 was injectedbetween the substrates by an injection method.

The pixel electrode layer and the common electrode layer were formedusing indium tin oxide containing silicon oxide (ITSO) by a sputteringmethod. The thickness of each of the pixel electrode layer and thecommon electrode layer was 110 nm the width thereof was 2 μm, and thedistance between the pixel electrode layer and the common electrodelayer was 2 μm. Further, an ultraviolet light and heat curable sealantwas used as the sealant. As curing treatment, ultraviolet light(irradiance of 100 mW/cm²) irradiation was performed for 90 seconds, andthen, heat treatment was performed at 120° C. for 1 hour.

Further, polymer stabilization treatment was performed on the liquidcrystal element of this example in the following manner: the liquidcrystal element was set at a given constant temperature within thetemperature range where a blue phase is exhibited, and irradiation withan ultraviolet light (light source: a metal halide lamp, wavelength: 365nm, irradiance: 8 mW/cm²) was performed for 30 minutes.

Further, voltage was applied to the formed liquid crystal element, andthe transmittance with respect to an applied voltage was evaluated. Thecharacteristic evaluation was performed with a liquid crystal evaluationsystem (LCD-7200 produced by Otsuka Electronics Co., Ltd.) under thefollowing conditions: a halogen lamp was used as a light source, thetemperature was set to room temperature, and the liquid crystal elementwas sandwiched, between polarizers in crossed Nicols.

FIG. 8 shows the relation between applied voltage and transmittance inthe liquid crystal element. The transmittance was measured on thecondition that the intensity of the light source is 100%. As shown inFIG. 8, it is found that the liquid crystal element of this example hasa high transmittance even at low applied voltage, so that low voltagedriving of the liquid crystal element is possible.

Consequently, a liquid crystal element in which the novel polymerizablemonomer compound in this example or a liquid crystal compositionincluding the polymerizable monomer compound is used is capable of lowvoltage driving. Thus, the power consumption of a liquid crystal displaydevice or an electronic apparatus including the liquid crystal elementcan be further reduced.

This application is based on Japanese Patent Application serial no.2011-104440 filed with Japan Patent Office on May 9, 2011, the entirecontents of which are hereby incorporated by reference.

What is claimed is:
 1. A compound represented by a formula (G1):

wherein n and m are 6, and both of R¹ and R² represent hydrogen or amethyl group.
 2. A composition comprising the compound according toclaim
 1. 3. A composition comprising: the compound according to claim 1;a nematic liquid crystal compound; and a chiral agent.
 4. Thecomposition according to claim 2, wherein the composition exhibits ablue phase.
 5. The composition according to claim 3, wherein thecomposition exhibits a blue phase.
 6. A liquid crystal display devicecomprising the composition according to claim
 2. 7. A liquid crystaldisplay device comprising the composition according to claim 3.